Not sure where you live but I have never lived in a city with a dozen restaurants with an 80+ year history with the same way of traditional food prep/ingredients. Restaurants have exceptionally short lives as it is a brutal industry, and supply chains have absolutely changed over 80 years.
I don't think we've lost anything; it's just that, in an era of cheap economies of scale from mass-production, artisanal anything (including artisanal cooking) is going to cost more—possibly enough to put most "authentic" / "traditional" cuisine out of reach of the working class, unless they're willing to make it themselves. (And who has the time for that?)
If you live in a city, look through restaurant reviews for a couple minutes and you'll probably be able to find a dozen local places in your own neighbourhood that have been open for 80 years or more, keeping up the tradition of serving the same food, the same way, that they always have. The only thing that such places have changed between then and now, are their prices.